Given a room with n people in it, what is the probability any two will have the same birthday?
[This article was first published on Jason Bryer » R, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Revisiting a fun puzzle I remember first encountering as an undergraduate. Nice example of creating a plot in R using ggplot2. I also plot the probability of someone in the room having the same birthday as you.
## See http://en.wikipedia.org/wiki/Birthday_problem for an explanation of the problemrequire(ggplot2)require(reshape)
theme_update(panel.background=theme_blank(), panel.grid.major=theme_blank(), panel.border=theme_blank())
birthday <- function(n) { 1 - exp( - n^2 / (2 * 365) )}
myBirthday <- function(n) { 1 - ( (365 - 1) / 365 ) ^ n}
d = 200df = data.frame(n=1:d, AnyTwoSame=birthday(1:d), SameAsMine=myBirthday(1:d))df = melt(df, id.vars='n')
ggplot(df, aes(x=n, y=value, colour=variable)) + geom_line() + scale_colour_hue('') + xlab('Number of People in Group') + ylab('Probability')
To leave a comment for the author, please follow the link and comment on their blog: Jason Bryer » R.
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.